1. Technical Field of the Invention
This invention relates to an improved method for the manufacture of high molecular weight polyoxyalkylene amines. More particularly, this invention relates to a method wherein a high molecular weight hydroxyterminated polyoxyalkylene compound is reacted with ammonia in the presence of hydrogen and Raney nickel/aluminum under reductive amination conditions to provide the corresponding polyoxyalkylene amine in good yield and selectivity.
It has been unexpectedly discovered in accordance with the present invention that when Raney nickel/aluminum (i.e., a nickel/aluminum alloy leached with a base, such as sodium hydroxide, to only partially leach the aluminum from the alloy, such that the final product contains from about 60 wt. % to about 75 wt. % of nickel and, correspondingly, from about 25 wt. % to about 40 wt. % of aluminum) is used as the catalyst for the reductive amination of hydroxy-terminated polyoxyalkylene compounds having a molecular weight of about 500 or more, there is a significant improvement in yield and selectivity, as compared with the yields and selectivities normally obtained when reductively aminating corresponding lower molecular weight hydroxy-terminated polyoxyalkylene compounds in the presence of Raney nickel/aluminum.
Although the reductive amination process of the present invention can be conducted batchwise using powdered Raney nickel/aluminum, in accordance with a preferred embodiment of the present invention, the reductive amination process is conducted on a continuous basis using a fixed bed of nuggets of the Raney nickel/aluminum, such as for example, nuggets of Raney nickel/aluminum having a particle size of about 1-10 mm in the longest dimension, a surface area of not more than about 25 m.sup.2 /gm and a porosity of about 0.01 to about 0.03 cc/gm. In accordance with a preferred form of the present invention, a hydroxy-terminated polyoxyalkylene compound, such as a diol or a triol, having a molecular weight of about 500 to about 10,000 is continuously passed through a bed of Raney nickel/aluminum nuggets in the presence of hydrogen and ammonia under anhydrous reductive amination conditions to provide the corresponding polyoxyalkylene diamine or triamine in good yield and selectivity.
2. Prior Art
Lee et al. U.S. Pat. No. 3,236,895 discloses a process for producing polyoxyalkylene polyamines such as polyoxyalkylene diamines by reacting a polyoxyalkylene diol with ammonia in the presence of hydrogen. Examples 8-14 are specifically directed to the reaction of a polypropylene glycol with ammonia in the presence of added hydrogen and a conventional Raney nickel catalyst. The yield of desired product range from about 40 to about 70%.
Horlenko et al. U.S. Pat. No. 3,215,742 also discloses the preparation of alkylene diamines, and more particularly, the preparation of hexamethylene diamine from 1,6-hexanediol by reacting the diol with ammonia in the presence of Raney nickel.
Zech U.S. Pat. No. 3,347,926 discloses an ammonolysis process for preparing aliphatic amines from hydroxy-containing feedstocks with an aminating agent in the presence of a Raney nickel catalyst containing a minor amount of chromium.
Yeakey U.S. Pat. No. 3,654,370 is directed to a process for the preparation of polyoxyalkylene polyamines wherein a polyoxyalkylene polyol is reacted with ammonia in the presence of hydrogen and a catalyst prepared by the reduction of a mixture of the oxides of nickel, copper and chromium.
European patent application No. 0022532 discloses the use of pelleted Raney nickel in a continuous process for the reductive amination of a low molecular weight compound such as neopentyl alcohol to provide the corresponding neopentyl amine. The normally to be expected low yields and selectivies are reported.
European patent application 0081701Al discloses the use of conventional Raney nickel in the amination of a 6000 molecular weight polyether triol. Conversion to amino groups is only 80%.